Printing a pdf is sometimes a bit tricky. Here are some useful tips:
BEFORE PRINTING CARDS (or other pdf's where size matters):
To make sure they print correctly, when you push the print button in adobe and the print box pops up with a small preview of the pdf on the right, look to the left side where it says page scaling with a drop down menu next to it. Make sure "none" is selected in the drop down menu. This should keep the cards centered. I also recommend printing them on white cardstock. Then simply cut them in half to make them 5.5 by 8.5 inches and fold them in half. They will fit perfectly in an A2 size envelope which you can purchase at any stationary store, and most office supply stores.